The present invention relates to a dome switch provided with a front sheet having dome-shaped protuberances, a spacer sheet and a circuit body, and more particularly, to a dome switch having a distinctive spacer sheet.
FIG. 19 is an exploded perspective view showing a related-art poly-dome switch (dome switch); FIG. 20 is a cross-sectional view showing the principal part of the dome switch before the switch is actuated; and FIG. 21 is a cross-sectional view showing the principal part of the dome switch when the switch is actuated.
A related-art poly-dome switch (dome switch) 1 used in a household electrical appliance is constituted by a front sheet 2, a spacer sheet 3, a flexible printed circuit (FPC) 4 and an adhesive sheet 5. The dome switch 1 is fixed through the adhesive sheet 5 to a plate 6 serving as a mount member.
A plurality of dome-shaped protuberances 7 which can be inverted inward are formed on the front sheet 2 so as to protrude outside. An electrode 8 (see FIG. 13) for the FPC 4 is provided on the interior surface of each protuberance 7.
The spacer sheet 3 is a thin sheet material and is provided for preventing occurrence of deformation of the front sheet 2. An adhesive layer is provided on the front and back of the spacer sheet 3 and enables fixation of the front sheet 2 and the FPC 4. A plurality of through holes 9 are formed at positions on the spacer 3 corresponding to the protuberances 7. Slit-like air release sections 10 are formed between the through holes 9.
The FPC 4 is a circuit member having a plurality of circuits to be designed into a desired pattern. A plurality of contact points 11 with which the electrodes 8 are to be brought into contact are provided on the spacer sheet 3. The FPC 4 is fixed to the adhesive sheet 5 by use of an adhesive. The adhesive sheet 5 has the function as a reinforcement member.
As shown in FIG. 21, according to the construction of the above-mentioned poly-dome switch 1, when any one of the protuberances 7 is depressed, the thus-depressed protuberance 7 becomes inverted toward the FPC 4. As a result, the electrode 8 is brought into contact with the contact point 11, thereby bringing the circuit into conduction. Since the poly-dome switch 1 is used in a household electrical appliance, and a user actuates the switch while viewing the same, ensuring a small stroke dimension (or a short stroke) for the protuberance 7 at the time of actuation of the switch has been sufficient.
The following problems are encountered in utilizing the related-art poly-dome switch 1 as a switch for equipment mounted on a vehicle; e.g., an automobile.
Since switching operation is frequently performed during a driving operation, actuating a switch with visual observation of the same in the manner as mentioned previously is not allowed, because of safety concerns. Accordingly, the poly-dome switch must be structured such that a sufficient stroke dimension of the protuberance 7 is ensured so as to enable a user to ascertain actuation of the switch without visual observation. However, structural limitations are imposed on ensuring a stroke dimension by increasing the protruding height of the protuberance 7.
The present invention has been conceived against the foregoing backdrop and aims at providing a dome switch which enables an increase in the stroke of a protuberance.
In order to solve the aforesaid object, the invention is characterized by having the following arrangement.
(1) A dome switch including:
a front sheet;
a dome-shaped protuberance which is formed on the front sheet, so as to protrude outside, can be reversed inside and includes an electrode provided therein;
a circuit member having a contact point with which the electrode are brought into contact when the protuberance is reversed; and
a spacer sheet for preventing occurrence of deformation of the front sheet, which is interposed between the front sheet and the circuit member, includes a through hole formed therein for ensuring contact between the electrode and the contact point and ensuring a stroke dimension of the protuberance.
(2) The dome switch according to (1), wherein the spacer sheet is constituted by a plurality of layers.
(3) The dome switch according to (1), wherein
the spacer sheet is constituted by an uppermost layer spacer sheet and at least one lower layer spacer sheet, and
the uppermost layer spacer sheet facing the front sheet is used for finely adjusting the stroke dimension and is formed thinner than the at least one lower layer spacer sheet.
(4) The dome switch according to (1), wherein
a plurality of the protuberances are formed on the front sheet, and
a plurality of the through holes corresponding to the plurality of the protuberances are formed on the spacer sheet.
(5) The dome switch according to (4), wherein
the plurality of the through holes are communicated each other through at least one air release section formed through the spacer sheet.
(6) The dome switch according to (5), wherein
the spacer sheet is constituted by an uppermost layer spacer sheet and at least one lower layer spacer sheet,
the at least one air release section are formed in the at least one lower layer spacer sheet other than the uppermost layer spacer sheet facing the front sheet.
(7) The dome switch according to (1), wherein
the spacer sheet is constituted by an uppermost layer spacer sheet and at least one lower layer spacer sheet, and
the through hole formed in the uppermost layer spacer sheet facing the front sheet are formed so as to become greater in diameter than the protuberance, and
the through hole formed in the at least one lower layer spacer sheet is formed so as to become greater in diameter than the through hole formed through the uppermost spacer sheet.
(8) A dome switch comprising:
a front sheet;
a dome-shaped protuberance which is formed on the front sheet so as to protrude outside, can be reversed inside, and includes an electrode provided therein;
a circuit member having a contact point with which the electrode are brought into contact when the protuberance is reversed;
a spacer sheet which is interposed between the front sheet and the circuit member and includes a through hole formed therein for ensuring contact between the electrode and the contact point;
an adhesive sheet including at one side thereof a circuit member attachment surface to be adhered to the circuit member and at the other side an adhesive fixing surface to be attached to a mount member including a space section formed in a mount surface thereof; and
a air release hole, formed through the adhesive sheet, which communicates the space section with the through hole for air release at the time of reversal of the protuberance when the adhesive sheet adheres the circuit member to the mount member.
(9) The dome switch according to (8), wherein
a plurality of the protuberances are formed on the front sheet, and
a plurality of the through holes corresponding to the plurality of the protuberances are formed on the spacer sheet.
(10) The dome switch according to (9), wherein
the plurality of the through holes are communicated each other through at least one air release section formed through the spacer sheet.
(11) The dome switch according to (10), where in the air release hole is communicated with the at least one air release section.
(12) A dome switch comprising:
a front sheet;
a plurality of dome-shaped protuberances which are formed on the front sheet so as to protrude outside, can be reversed inside, and each include an electrode provided therein;
a circuit member having a plurality of contact points with, each of the contact points being brought into contact with the corresponding electrode when the corresponding protuberance is reversed;
a spacer sheet which is interposed between the front sheet and the circuit member and includes a plurality of through holes, respectively corresponding to the plurality of protuberances, formed therein for ensuring contact between the electrode and the plurality of contact points, the spacer sheet including,
an uppermost layer spacer sheet, and
at least one lower layer spacer sheet interposed between the uppermost layer spacer sheet and the circuit member, wherein the plurality of through holes are communicated each other through at least one air release section formed through the at least one lower layer spacer sheet; and
an adhesive sheet including at one side thereof a circuit member attachment surface to be adhered to the circuit member and at the other side an adhesive fixing surface to be attached to a mount member
(13) The dome switch according to (12), wherein
the adhesive sheet includes a air release hole which communicates a space section formed in a mount surface of the mount member with the through hole for air release at the time of reversal of the protuberance.
According to the present invention, when one of the protuberances is depressed at the time of actuation of the switch and becomes reversed, the electrode provided on the interior surface of the protuberance is brought into contact with the contact point of the circuit member via the through hole formed in the spacer sheet. The spacer sheet acts as a member for preventing occurrence of deformation of a front sheet, as well as acting as a member for ensuring a stroke dimension of the protuberance. Accordingly, in order to increase a stroke of the protuberance, the only requirement is to increase the thickness of the spacer sheet within a range in which the protuberance can return to its original state. As a result, the depth of the through hole becomes greater, and the stroke dimension of the protuberance can be made greater. Naturally, deformation of the front sheet is prevented. The spacer sheet has an important function for maximizing the stroke of the protuberance.
According to the present invention, the dome switch is constituted of a spacer sheet made of a plurality of spacer sheets. As a result, the thickness of the spacer sheet can be changed, by means of changing, e.g., the number of layers, thereby facilitating adjustment of stroke dimension of a protuberance. Further, the poly-dome switch can possess more flexibility than can a poly-dome switch constituted of a single layer.
According to the present invention, the dome switch is constituted of a spacer sheet made of a plurality of spacer sheets. As a result, the thickness of the spacer sheet can be changed, by means of changing, e.g., the number of layers, thereby facilitating adjustment of stroke dimension of a protuberance. There is formed a dome switch, wherein the uppermost spacer sheet facing the front sheet is formed thinner than one or a plurality of lower-layer spacer sheets.
According to the present invention, the dome switch is constituted of a spacer sheet made of a plurality of spacer sheets. As a result, the thickness of the spacer sheet can be changed, by means of changing, e.g., the number of layers, thereby facilitating adjustment of stroke dimension of a protuberance. There is yielded a dome switch, wherein no air release section is formed in the uppermost layer spacer sheet facing the front sheet. As a result, there is obviated from the front sheet an edge, which would otherwise be caused by the air release sections. Hence, the front sheet can be protected when the protuberance is reversed. There can be minimized deformation of the front sheet, which arises in the periphery of the through hole when the protuberance is reversed. Since the air release sections are formed in one or a plurality of lower-layer spacer sheets, there is maintained a tactile click which arises at the time of actuation of the switch.
According to the present invention, the dome switch is constituted of a spacer sheet made of a plurality of spacer sheets. As a result, the thickness of the spacer sheet can be changed, by means of changing, e.g., the number of layers, thereby facilitating adjustment of stroke dimension of a protuberance. There is formed a dome switch, wherein limitations are imposed on the diameter of each through hole formed in the spacer sheet. As a result, there can be minimized deformation of the front sheet, which arises in the periphery of the through hole when the protuberance is reversed.
According to the present invention, when a protuberance is reversed toward the circuit member as a result of actuation of the switch, air which has remained inside the protuberance thus far escapes to the air release section of the spacer sheet via the through holes formed in the spacer sheet. The air release section is in communication with the space section of the mount member via the air release holes formed in the circuit member and those formed in the adhesive sheet. The space section of the mount member is utilized as a space for air release purpose at the time of reversal of a protuberance.
According to the present invention, when a protuberance is reversed toward the circuit member as a result of actuation of the switch, air which has remained inside the protuberance thus far escapes to the air release section of the spacer sheet via the through holes formed in the spacer sheet. Unlike the through holes of the lower-layer spacer sheets, the through holes of the uppermost spacer sheet are not provided with the air release section. Hence, at the time of actuation of the switch, no deformation or deformation arises in the front sheet in the periphery of the through hole. Further, unlike the through holes of the lower-layer spacer sheets, the through holes of the uppermost spacer sheet are not provided with the air release section. Hence, the through holes of the lower-layer spacer sheets can be made larger in diameter than those of the uppermost spacer sheet, thus broadening the space for air release purposes.
According to the present invention, the air release section of the lower-layer spacer sheets is in communication with the space section of the mount member via the air release holes formed in the circuit member and those of the adhesive sheet. The space section of the mount member is utilized as a space for air release purposes at the time of reverse of a protuberance.